public async Task WhenCalled_ReturnsValidateOnPasswordHasher()
                {
                    var helper = new FakeUserHelper1();

                    helper.FakePasswordHasher.Validate_Output =
                        new PasswordValidateResult(valid: true);
                    var user = new User()
                    {
                        PasswordHash = "hash"
                    };

                    var result = await helper.ValidatePassword(user, "password");

                    Assert.Equal(helper.FakePasswordHasher.Validate_Output, result);
                }
                public async Task WhenCalled_CallsValidateOnPasswordHasher()
                {
                    var helper = new FakeUserHelper1();

                    helper.FakePasswordHasher.Validate_Output =
                        new PasswordValidateResult(valid: true);
                    var user = new User()
                    {
                        PasswordHash = "hash"
                    };

                    await helper.ValidatePassword(user, "password");

                    Assert.Equal(user.PasswordHash,
                                 helper.FakePasswordHasher.Validate_InputHash);
                    Assert.Equal("password",
                                 helper.FakePasswordHasher.Validate_InputPassword);
                }